Kiln Installation Instructions

How to Size the Electrical Circuit:

1. See hotkilns.com/support/pottery-kiln-knowledgebase/what-amperage-fuses-or-circuit-breaker-do-you-need-fuse-kiln

Voltage:

1. L&L makes kilns for 208 volts, 220 volts, 240 volts, 380 volts, and 480 volts.
2. Ensure the kiln is connected to the correct voltage.
3. A 208-volt kiln on a 240-volt supply will generate too many amps and may cause a fire.
4. A 240-volt kiln on a 208-volt supply will heat 25% slower and may not reach higher temperatures.
5. Connecting a single-phase kiln to two legs of a three-phase supply causes an unbalanced load. Consult a qualified electrician. Use a three-phase kiln for a three-phase supply.
6. All L&L kilns have a ground wire, which is not used as a neutral.
7. Properly ground the kiln using the ground wire to ensure safety and control operation.

Hooking Up to Power:

1. Most L&L kilns under 48 amps include a 6-50P plug (single phase) or a 15-50P plug (three phase). Kilns for markets outside North America do not include a cord.
2. Have an electrician install the proper receptacle and safety switch. Ensure fuse ampere capacity and power lines are adequate.
3. Follow lockout/tagout procedures in industrial or institutional settings.

Direct Hook-Up Kilns:

1. Kilns over 48 amps are directly wired to a fused disconnect or circuit breaker panel.
2. Some kilns under 48 amps are also direct hook-up.

Changing to Direct Hook-Up:

1. L&L power cords are rated for 105°C. Lower-rated cords can malfunction and cause fires.
2. Removing the plug and direct wiring the kiln is acceptable and will not void the warranty. Use connection wires rated for at least 105°C.

Installing a Plug Receptacle:

1. If the kiln comes with a plug, install the receptacle so the cord hangs down, not up.
2. Ensure the plug seats securely in the receptacle to avoid overheating and corrosion.

Plugs:

1. L&L uses UL-listed NEMA 6-50P or 15-50P plugs and cords, rated for 50 amperes at up to 250 volts AC. The current-carrying conductors are 6 AWG, and the grounding conductor is 8 AWG.

2. This is a 6-50P Plug Configuration for single phase Easy-Fire and School-Master kilns.

3. This is a 15-50P Plug Configuration for three phase Easy-Fire and School-Master kilns

Note about Plug and Fuse Ratings:

1. L&L Kiln uses a UL listed NEMA 6-50P or 15-50P plug and cord that is robustly designed, and marked for 50 amperes at up to 250 Volts AC, 1 Phase (or 3 phase for the 15-50P), with a grounding prong. The (2 or 3) current carrying conductors are 6 AWG, which according to the 2002 NEC (National Electrical Code) Table 400.5 for flexible cables have an allowable ampacity of 55 amperes, and the grounding conductor is 8 AWG, which does not normally carry any current. The plug, or cap, is designed and constructed so that there are no exposed current-carrying parts except for the prongs, which only carry current when the plug or cap is safely inserted into its mating receptacle.
2. This plug and cord set is UL listed for carrying 50 amperes at the proper voltage and phase. All L&L kilns which use these plugs and cords are also UL listed as complete appliances, with the ratings as listed in L&L Kiln Mfg, Inc., catalogs. When installed, the circuit that supplies power to the kiln must be designed per NEC requirements, and in many cases must be provided with conductors and overcurrent protection rated for 60 amperes, or 125% of the ampere listing of the kiln. (E.g., the E23T is listed at 48 amperes. 48 * 1.25 = 60 ampere rating for overcurrent protection and power supply conductor rating.) This may initially create some confusion, but remember that the kiln is UL listed with the NEMA 6-50P plug and cord set as a component of the appliance - it is the power supply circuit that must be protected at 125% of the listed rating, not the individual components inside the appliance.

Protect Power Cord from Kiln Case:

1. Route the cord away from the hot kiln case and secure it to prevent contact. Contact with the hot case can cause melting, short circuits, or fires.

Use a Fused Disconnect:

1. Install a separate fused disconnect box with a lockout provision near the kiln.
2. This allows easy power shutoff and prevents unauthorized use.
3. Frequent unplugging can weaken outlet spring tension. A fused disconnect switch provides a reliable power-off method.

Locate Kiln Within 50 Feet of Breaker:

1. Position the kiln within 50 feet of the breaker box. Longer runs may require larger hook-up wires. Ensure a licensed electrician follows the National Electrical Code.

Fusing Your Circuit:

1. Have an electrician follow the National Electric Code and local requirements. The kiln's full load amps are listed on the data nameplate.

Use Proper Grounding:

1. Ensure proper grounding and testing by an electrician.
2. Grounding can be to a cold water pipe or system ground in the building. Proper grounding prevents electrocution and handles high voltage safely.
3. Replace any deteriorated wires due to heat and wear over time.

Use the Proper Wire Gauge:

1. Refer to electrical specifications for hook-up wire sizes, which vary by ambient temperature and wire length.
2. Running power over long distances results in voltage drops. These estimates are dependent on the kiln operating at 50% to 100% of its capacity, with the temperature of the wire no more than 167°F.

• 7 volts per 100 feet with 10 awg wire
• 21 volts per 300 feet with 10 awg wire
• 6 volts per 100 feet with 6 awg wire
• 18 volts per 300 feet with 6 awg wire
• 3 volts per 100 feet with 1 awg wire
• 9 volts per 300 feet with 1 awg wire

Use Copper Wire for Hook-Up:

1. Do not use aluminum wire. Aluminum wire can cause oxidation, leading to overheating and fires. Braided copper wire is preferred.
2. This is of particular importance with kilns not to use aluminum wire for the hook ups.
3. The specific reason particular to kilns is that the wire tends to get hotter near the kiln than it might going into some other types of appliance.
4. Also, being a resistive load, there is constant heat being generated by the conductors.
5. When aluminum wire gets hot it accelerates oxidation. Aluminum oxide is a resistor; copper oxide is not as much. If the connection at the terminal board gets oxidized it will really heat up - to the point where it could cause a fire.
6. Braided copper wire is preferred.

Do Not Use Extension Cords:

1. Only use extension cords for the 120-volt vent system.
2. Do not use high-power extension cords for the kiln. 
3. A long wire can act as a resistor and get hot.

Off-Peak Electrical Usage:

1. Some utilities offer special rates for running energy-intensive appliances like kilns during off-peak hours.
2. Check with your local utility. This would require a special time-of-use electrical meter.

Where to Get More Information:

1. See ELECTRICAL THEORY AND APPLICATION FOR ELECTRIC KILNS for a complete description of electrical theory, fusing, hook-up wire sizes, etc. as they apply to kilns.
2. Refer to hotkilns.com/support/electrical-troubleshooting for basic electrical information.

Electrical Specifications:

1. See your wiring diagram and data nameplate for voltage and amperage requirements.

Balanced Three Phase Circuits

1. Three-phase circuits are balanced on kilns with three sections (27" high). This is not true for 18", 22", 36" or 45" high kilns unless they are specially designed.